(CNN) -- UK Prime Minister Gordon Brown has branded the cholera crisis in Zimbabwe "an international emergency" and called on the world community to confront President Robert Mugabe, leader of the central African nation.

A shortage of clean drinking water has unleashed a cholera epidemic in Zimbabwe.

"This is now an international rather than a national emergency," Brown said in a statement Saturday. "International because disease crosses borders. International because the systems of government in Zimbabwe are now broken. There is no state capable or willing of protecting its people."

Earlier this week the government of Zimbabwe, which already suffers from severe economic problems and political instability, declared a national emergency following the outbreak, which has so far killed more than 600 people.

Cholera, a water-borne disease, is on the increase in nine of Zimbabwe's 10 provinces, the U.N. Office for the Coordination of Humanitarian Affairs (OCHA) warned. It blamed "poor water and sanitation supply, a collapsed health system and limited government capacity to respond to the emergency."

Many of those afflicted with the disease have fled to neighboring countries to seek medical help -- which risks spreading the outbreak still further.

Brown called on the international community to tell Mugabe "enough is enough," and suggested that the United Nations Security Council meet to discuss the issue.

He added that the most pressing issue was to ensure that testing and rehydration equipment and packs reach the right people, as well as for aid agencies to set up a organizational structure in the state capital Harare to confront the disease.

"The people of Zimbabwe voted for a better future. It is our duty to support that aspiration," Brown added.

Brown's comments came one day after U.S. Secretary of State Condoleezza Rice said that the outbreak is the latest sign that Mugabe's rule over the country must end.

"It's well past time for Robert Mugabe to leave. I think that's now obvious," Rice said during a visit to Denmark.

Washington has long called for Mugabe to leave office, with President George W. Bush calling Zimbabwe's runoff presidential election in June a "sham" and instructing Rice and other U.S. officials to develop additional sanctions against Mugabe's "illegitimate government."

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"The United States will always do anything and everything that it can to help innocent people who are suffering," Rice said. "And we are not going to deny assistance to people in need because of their government. But if this is not evidence to the international community that it's time to stand up for what is right, I don't know what will be. And frankly, the nations of the region have to lead it."

Rice -- who has just about a month left in office before President-elect Barack Obama's administration takes over -- also called on all African nations to speak up.

Asked whether the United States and Europe should try to force out Mugabe, Rice responded, "Well, without help in the region, it's very difficult to have the tools that will bring about a just resolution in Zimbabwe. The United States and Europe can't do everything alone. Other states are responsible too. And the southern African states should be the most responsible at this point, because they have the most at risk. And the people of Zimbabwe have suffered long enough."

Supporters of Mugabe, who has come under heavy international criticism for several years, were accused of political intimidation following June's presidential runoff vote.

For months there have been some efforts to build a power-sharing government between Mugabe's ruling Zanu PF party and the opposition movement for Democratic Change, led by Morgan Tsvangirai, to little avail.

On Thursday, Mugabe hinted he may form a Cabinet without the opposition and call for early elections. The opposition responded that it would welcome a "genuine election," with international supervision.

The 84-year-old Mugabe, who has led Zimbabwe since its independence in 1980 from Great Britain, also suggested he would ignore an international tribunal ruling that declared illegal his government's seizure of farms from white Zimbabweans.